This application claims priority of European Application No. 02405094.0 filed Feb. 11, 2002, entitled Annual Date Mechanism for Clock Movement.
1. Field of the Invention
The present invention relates to an annual date mechanism for a clock movement comprising a date indicating runner with thirty-one positions engaged once a day with a drive runner in kinematic connection with the geartrain of said clock movement, an annual cam, the contour of which is shaped to distinguish the thirty-one-day months from the other months, means for driving this cam by one revolution per year and a correction mechanism connected to said annual cam to advance said indicating runner by one additional position at the end of each month of less than 31 days.
This type of date mechanism which is a compromise between the simple date and the perpetual or semi-perpetual date involving a relatively complicated and therefore tricky mechanism made up of a fairly large number of parts, occupying a great deal of space both in the plane and in terms of height, has long been proposed. The simple date mechanism entails resetting the date five times per year, at the end of the months containing less than 31 days. The annual date requires just one correction, at the end of the month of February.
2. Description of the Related Art
Among date mechanisms of this type, mention may be made of CH 583 932, CH 684 815, CH 685 585, EP 756 217, CH 581 341 and EP 987 609. All these mechanisms have a trailing date change, furthermore, the passage between xe2x80x9c30xe2x80x9d and xe2x80x9c1xe2x80x9d takes place through a two-phase jump thus causing xe2x80x9c31xe2x80x9d to appear for some length of time between the xe2x80x9c30xe2x80x9d and the xe2x80x9c1xe2x80x9d at the end of months of under 31 days. Furthermore, some of the aforementioned mechanisms are relatively complicated. Date mechanisms with instantaneous jump are also known, but these are simple dates.
The object of the present invention is to render annual a simple date mechanism, preferably instantaneous, using a solution which adds as few additional parts as possible, thus guaranteeing reliable operation and small bulk.
To this end, the subject of the present invention is a date mechanism of the aforementioned type, as defined by claim 1.
The main advantages of this mechanism lie in its simplicity and in its efficiency and its reliability. Advantageously, this mechanism may be associated with an instantaneous jump date mechanism and allows automatic correction at the end of months of under 31 days in a way which is also instantaneous.